1. Field of the Invention
The present invention relates to a backlight assembly and a display device having the backlight assembly. More particularly, the present invention relates to backlight assembly capable of controlling light-emitting elements (diode chips) for color-specific dimming and a display device having the backlight assembly.
2. Description of the Related Art
Liquid crystal display (LCD) devices typically include a backlight assembly for providing white light to pass through the LCD layer and color filters of the display device so that the display device may display an image. Examples of a white light source that may be used for the backlight assembly include a cold cathode fluorescent lamp (CCFL), a plurality (array) of light-emitting diodes (LED), etc.
Originally, a conventional backlight assembly for an LCD display continuously generates light while a power source is applied to the backlight assembly, without being synchronized with the image displayed. However, active research has been conducted on dimming-type backlight assemblies controlling brightness depending on the brightness of a displayed image in order to improve the power consumption of a backlight assembly and the image contrast.
Conventional methods of dimming a backlight assembly now include a 0-dimensional (0-D) dimming method, a 1-dimensional (1-D) dimming method, and a 2-dimensional (2-D) dimming method, etc. The 0-D dimming method controls (dynamically varies) the brightness of the entire display screen. The 1-D dimming method controls (dynamically varies) the brightness of each line of a display screen. The 2-D dimming method, which is called local dimming, independently controls (dynamically varies) the brightness of each portion of a display screen.
As requirements for color reproduction are increasing, active research is being conducted in color dimming, that is, color-selective dimming. An optical feedback system for detecting and controlling the amounts of light exiting from each of a red LED, a green LED and a blue LED is required for performing the conventional color dimming. The feedback system requires a sensor, and a light sensor is generally used as the sensor.
The feedback system employing the light sensor receives light emitted from an LED to generate a voltage signal, and the feedback system uses the voltage signal as a feedback signal to control the LED. However, the red, green and blue LEDs have to hold their light emissions at a fixed level for the feedback system using the light sensor.
The brightness sensed by a light sensor provided for controlling local dimming may be varied depending on the image displayed, and the brightness and the color sensed by a sensor for color dimming may be varied depending on the image signal. The feedback system using the light sensor may not be easily implemented in the local dimming method or the color dimming method because of the requirement to hold light emissions at a fixed level.